<!DOCTYPE html>
<html lang="zh">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    /* 实际开发中会遇到冗余代码的抽取（可将一些公共的代码抽取到一个公共的类中去） */
    /* p {
      font-size: 40px;
      color: red;
    }

    div {
      font-size: 40px;
      color: red;
    } */
    .common {
      font-size: 40px;
      color: red;
    }
  </style>
</head>

<body>
  <p class="common">我想变大，也想变红</p>
  <div class="common">我也想变大，也想变红</div>
</body>

</html>